U.S. Pat. No. 4,077,213 issued to applicant in 1978. In that patent, applicant discloses a wave driven generator wherein a plurality of different sized floats were connected into an array through nonlinear interfaces so their relative motion drives hydraulic pumping means to generate electricity. In that application, which is herein incorporated by reference, the individual floats of the wave driven generator power absorbing array were sized so as to present a "black body" or "Hagen Array" to ocean waves incident upon them.
When wave energy impinges upon a floating object, the energy is split three ways. A first portion is absorbed by the object if the object's motion is resisted, as it would be in wave generator functionally adapted to drive a prime mover. Any single float will probably not absorb more than about one-third of the energy incident upon it. A similar amount is reflected. The amount of energy reflected from a given float depends on the physical characteristics of the float such as its mass, size and shape and the amount of resistance or "back pressure" the incident wave experiences when it moves the float. Yet another increment of wave energy is transmitted through whatever structure the float is attached.
One of the objects of U.S. Pat. No. 4,077,213 was to provide a wave generating system wherein the float array absorbed virtually all of the energy impinging on it over a broad bandwidth of ocean waves. Applicant Hagen's co-pending application filed simultaneously with this application, discusses a wave generating array capable of absorbing more energy than impinges upon the array directly.
On Apr. 23, 1979 applicant filed for reissue of U.S. Pat. No. 4,077,213. This reissue application, Ser. No. 032,162, has issued on Dec. 28, 1982 as U.S. Pat. No. Re 31,111.
Part of applicant's development program for commercializing his earlier invention was to estimate the construction costs for a 1 MW and 3 MW pilot plant constructed according to the teachings of U.S. Pat. No. 4,077,213. It quickly developed that one of the most important cost drivers affecting system design was the mooring system adopted for use with the invention. All conventional large float array mooring systems, such as the one disclosed in U.S. Pat. No. 4,013,382 rely on a complex network of overhead frame sections. This type of mooring is extremely expensive, costing between $500 and $1,000 per kilowatt of installed generating capacity for the Hagen array, i.e. the invention disclosed in U.S. Pat. No. 4,077,213.
Aside from being relatively expensive, the preferred embodiment shown in the earlier patent would be difficult to service if a plurality of generator modules were installed at the same location. This would be true because a float in the middle of the array might need servicing and it would be quite difficult to get a ship or crew to the float to do the servicing. It would be desirable to allow boats to pass between the floats in order to do routine servicing on the float array.
Array support structures projecting above the surface of the water also suffer from vulnerability to adverse weather, i.e. hurricanes and the like. Finally, from a purely aesthetic standpoint, they are profoundly ugly.
Over the past decade great progress has been made by the petroleum industry in the fabrication, construction, implacement and operation of large subsea structures. The largest use of these structures has been for oil rigs operating in relatively shallow water. Recently some subsea structures have been implaced in as much as 500 feet of water. Current anti-corrosion coatings and cathodic protection systems are sufficiently advanced to insure a sufficiently long life to make an underwater support system commercially feasible. This underwater system would also be physically attractive, environmentally beneficial, and would allow access to any part of the array for maintenance.
As model tank tests and small scale sea tests of the Hagen array were conducted during applicant's development program, data accumulated to the effect that the wave energy reflected from larger floats in the array was quite significant. The present invention is one way of providing a large number of intermediate and small size floats in the Hagen array whereby this reflected wave energy may be efficiently captured even in relatively low sea states.
It is therefore an object of the present invention to provide an array wherein reflected power is fluid coupled between a plurality of varying sized floats without direct physical connections between the floats.
Another object of the present invention is to provide a Hagen array that is accessible to maintenance ships.
A further purpose of the present invention is to provide a Hagen array that is physically attractive and can be used by pleasure boaters for fishing and the like.
Yet another purpose of the present invention is to provide a Hagen array wherein the individual floats of the array are coupled directly to a substructure that forms an artificial reef, which will attract fish and the like.
A final purpose of the present invention is to provide an alternative means of generating very large amounts of baseload electric power that a positive environmental impact.